Characterization of Salix nigra floral insect community and activity of three native Andrena bees

Salix nigra (black willow) is a widespread tree that hosts many species of polylectic hymenopterans and oligolectic bees of the genus Andrena. The early flowering time of S. nigra makes it an important nutritive resource for arthropods emerging from hibernation. However, since S. nigra is dioecious, not all insect visits will lead to successful pollination. Using both visual observation and pan-trapping we characterized the community of arthropods that visited S. nigra flowers and assessed the differences among male and female trees as well as the chemical and visual drivers that influenced community composition across three years. We found that male trees consistently supported higher diversity of insects than female trees and only three insect species, all Andrena spp., consistently visited both sexes. Additionally, A. nigrae, which was the only insect that occurred more on female than male flowers, correlated strongly to volatile cues. This suggests that cross-pollinators cue into specific aspects of floral scent, but diversity of floral visitors is driven strongly by visual cues. Through time the floral activity of two Andrena species remained stable, but A. nigrae visited less in 2017 when flowers bloomed earlier than other years. When native bee emergence does not synchronize with bloom, activity appears to be greatly diminished which could threaten species that only subsist on a single host. Despite the community diversity of S. nigra flowers, its productivity depends on a small fraction of species that are not threatened by competition, but rather rapidly changing conditions that lead to host-insect asynchrony.

Sex determination through X-Y heterogamety in Salix nigra

The development of non-recombining sex chromosomes has radical effects on the evolution of discrete sexes and sexual dimorphism. Although dioecy is rare in plants, sex chromosomes have evolved repeatedly throughout the diversification of angiosperms, and many of these sex chromosomes are relatively young compared to those found in vertebrates. In this study, we designed and used a sequence capture array to identify a novel sex-linked region (SLR) in Salix nigra, a basal species in the willow clade, and demonstrated that this species has XY heterogamety. We did not detect any genetic overlap with the previously characterized ZW SLRs in willows, which map to a different chromosome. The S. nigra SLR is characterized by strong recombination suppression across a 2 MB region and an excess of low frequency alleles, resulting in a low Tajima’s D compared to the remainder of the genome. We speculate that either a recent bottleneck in population size or factors related to positive or background selection generated this differential pattern of Tajima’s D on the X and autosomes. This discovery provides insights into factors that may influence the evolution of sex chromosomes in plants and contributes to a large number of recent observations that underscore their dynamic nature.

Riqueza, composición y abundancia de especies en una comunidad vegetal ribereña en el río Santa Catarina, Monterrey, Nuevo León

La vegetación ribereña constituye un elemento clave para el mantenimiento de los ecosistemas fluviales, en especial, en aquellos que se encuentran circundados por zonas urbanas. El objetivo del presente trabajo fue evaluar la variación espacial de la riqueza, la composición y la estructura de la vegetación ribereña en un tramo del río Santa Catarina sobre dos municipios de la Zona Metropolitana de Monterrey. Para el análisis de la vegetación, se establecieron transectos de muestreo, en un tramo de 15.65 km. El estrato alto (plantas arbustivas y arbóreas), se analizó mediante un modelo de ordenación Bray-Curtis y una gráfica de dominancia-diversidad. Para el estrato bajo (plantas herbáceas), se utilizó el coeficiente de similitud de Jaccard. En el estrato alto, se registraron 16 familias pertenecientes a 25 géneros y 28 especies. Las especies con mayor número de individuos fueron Salix nigra, Leucaena leucocephala, Ricinus communis y Parkinsonia aculeata. La composición de la vegetación tiene una similitud de intermedia a alta, ya que los grupos variaron con valores de 60 % a 71.53 %. En el estrato bajo, se registraron 25 familias, 53 géneros y 60 especies, con una similitud de baja a intermedia, debido a que los primeros tres grupos variaron entre 23 % a 47 %. Las especies que se reportaron con mayor distribución en el estrato bajo, fueron Cyperus involucratus y Phragmites australis en 7 sitios cada una, Eragrostis mexicana, Heliantus annuus, Melinis repens, Polygonum pensylvanicum y Typha domingensis, en 6 sitios cada una. La composición de la vegetación se encuentra en un estado sucesional secundario, debido a que las especies con mayor presencia son introducidas, como Leucaena leucocephala y Ricinus communis para el estrato alto, y Cypereus involucratus y Melinis repens, para el estrato bajo.

Promising inhibition of krait snake’s venom acetylcholinesterase by Salix nigra and its role as anticancer, antioxidant agent

Snakebites are considered a neglected tropical disease that affects thousands of people worldwide. The available antivenoms are associated with numerous side effects. As an alternative, researchers have extensively studied the plants in order to obtain some unusual treatment. The current study was conceded to evaluate the effects of <italic>salix nigra</italic> (Black willow) against krait snake venom acetylcholinesterase and its role as anti-cancer, anti-oxidant agent. Standard protocols of Ellman, Meyer, Gyamfi and Ruch were used for enzyme inhibition, anti-cancer and free radicals scavenging assays respectively. The methanolic extract of <italic>Salix nigra</italic> proved to possess neutralization properties against krait snake (<italic>Bungarus Sindanus</italic>) venom acetylcholinesterase. Statistical data of the results showed that <italic>Salix nigra</italic> extract inhibited the krait venom acetylcholinesterase through concentration dependent manner. Kinetic analysis using Lineweaver Burk plot revealed that <italic>Salix nigra</italic> caused competitive type of inhibition i.e. <italic>k</italic>_{<italic>m</italic>} value increased while V_max remain constant with an increase of extract’s concentration. The calculated IC₅₀ value of <italic>Salix nigra</italic> was found to be 177μg/ml. In DPPH free radical scavenging assay, extract showed good scavenging potential with IC₅₀ value of 317μg/ml. Similarly, using H₂O₂ free radicals, the % scavenging of the extract at 100, 250, 500 and 1000μg/ml was 41, 54, 69 and 74% in comparison with ascorbic acid. Moreover, the extract exhibited good cytotoxic activity against brine shrimps in a dose dependent manner. The present work suggests, for the first time, that <italic>Salix nigra</italic> extract can be used not only as a potent inhibitor of snake venom acetylcholinesterase but also for the eradication of free radicals along with significant anticancer activity.